Multiplex radio telephony and telegraphy



J. H. HAMMOND. JR

MULTIPLEX. RADIO TELEPHONY AND TELEGRAPH! April 22, 1924. I 1,491,774-

Oiiginal Filed May 13, 1912 2 Sheets-Sheet 1 WITNESSES I dVH/TOR e5 M Y I M ATTORNEYS April 22 1924. v 1,491,774

1 H. HAMMOND. JR

.MULTIPLEX RADIO TELEPHONY AND TELBGKAPHY Original Filed May 13 1912 2 Sheets-Sheet 2 WITNESSES I/VI/E/VTOH ATTORNEYS I Patented Apr. 22, 1924 To-all whom it may concern:

UNITED STATES JOHN HAYS HAMMOND, .13., or cnoucns'rnn. MASSACHUSETTS.

MULTIPLEX name TELEPHGNY Ann TELEGRAPHY.

Application filed MaylS, 1912, Serial No. 696,899. Renewed December 11, 1918. Serial No. 266,362.

Be it known that I, JOHN HAYS HAM: MOND, J r., a citzien of the United States, residing at Gloucester, in the State-of Massachusetts, have invented certain newand useful Improvements in Multiplex Radio Telephony and Telegraphy, of which thefollowing is a specification.

My invention relates to systems for the simultaneous transmission and reception of a plurality of telephone and telegraph mes sages by means of radiant energy, and relates more particularly to systems in which. selectivity is secured by employing distinc-.

tive wave lengths and wave-group frequencies or periodic amplitude variations. In

such systems I secure a still higher degree of selectivity by using a combination of highfrequency waves and at least one series of wave groups or periodic amplitude variations for the transmission of telephone con- 'versations, and a combination of high-frequency waves and at least two series of wave groups or periodic amplitude variations for the transmission of telegraph signals, as is hereinafter more fully set forth and described.

In the accompanying figures:

Fig. 1 is a diagrammatic representation of a transmitting station constructed in accordance with the invention and including three diiierent arrangements of telephone and telegraph apparatus;

Fig. 2 shows a modification of part of the transmitting apparatus of Figure 1; Fig. 3 shows another modification of part of the transmitting apparatus of Figure 1; an

Fig. 4 shows a receiving station on my system, having three diflerent sets of cirwits and receiving apparatus.

In Figure 1 the alternating current gen erator G energizes the field winding F of the.

high-frequency alternator H, -thereby impressing periodic amplitude variations, which should have a frequency above the limits of audibility, upon the current from H. The switch S is used to connect the al ternator H with either the telephone transmitter T or the interrupter I and key K, ac-' cording as it is desired to send telephone or telegraph messages. In the former case, the high-frequency current from' H, with the amplitude variations due-to the generator G, will have telephonic vibrations superposed upon it by T, and then, by means of the rent'waves will be impressed upon the antenna A. When it is desired to send'telegraph messages, the switch S is connected with the interrupter I and the key K, the frequency of the interrupter being different from, and usually less than, the frequencies of the alternator H and the generator G. Telegraph signals are sent in the usual way by imeans of the key K, and the combined current wave is impressed upon the antenna A by means of the coupling coils L and L A second kind of transmitting apparatus is shown in the middle part of the figure where the oscillatory are 0 is supplied from a source of direct current N N through'the choke'coils X and Y. This arc produces oscillations in .the circuits 0 L L C and O L C the frequencies of these oscillations depending upon the values of the inductances L and L and L, and the capacities C and C respectively. These inductances .and capacities are so adjusted that high-frequency oscillations, of the order of hundreds of thousands per second, are produced in the circuit 0 L L C, and oscillations of alower frequency, but still above the limits of audibility, are produced in the circuit 0 L C. These oscillations in O L? C produce transmitter T or the interrupter I and key K "with the coil L, so that either telephone vibrations or telegraph signals can be impressed upon the circuit 0 L L (Land thence, by means of the coupling coils L and L upon the antenna A. The frequency of the interrupter I should be lower than the frequencies of the oscillatory arc circuits.

A third way of producing periodic am"- plitude variations in the transmitted waves 'is shown in the lower part of the figure,

where a motor M rotates the coil L so as to vary its mutual inductance with coil L, and 'so cause periodic amplitude variations in the high-frequency current induced in the c'oilL' by the alternator H In circuit with thealternator H and the coil L" is the switch S which can connect in the circuit either the telephone transmitter T or the interrupter I and the key K. The coil 1.. i

should be rotated at such a speed asto produce amplitude variations of a frequency above the limits of audibility, and the rotation of L afiects only its mutual relations 5 with coil L", and does not change its relation to the antenna A and the'coils- L and L In Figure 2, the switch S and key K, or the switch S and key K of Figure 1 are /replaced by the key K". In its normal position key K makescontact at U and so co1npletes the circuit from the alternator H through the telephone transmitter T and coupling coil L. In this position of the key K the circuit is ready for telephone messages. When it is desired to telegraph, key K is operated in the usual way. Contact at U is first broken, thus throwing the telephone T out of circuit, and contact is made at V, thus 7 completing the circuit through the interrupter I In Figure 3, the switch S and key K of Figure 1 are replaced in a similar manner b key K. In its normal position the key makes contact at U and completes the circuit from the battery J through the telephone transmitter T and the coil L When the battery J is used, this auxiliary circuit should be in inductive relation to the circuit supplying the are 0, so that, for m instance, the coil L is inductively coupled withthe coil X. When the apparatus shown in Figure 3 is used in inductive relation to the circuit 0 L L C, of Figure 1, the battery J can be omitted. For telegraphing,

85 the-key K is operated in the usual way,'f

first breakin contact at U and then making contact at 1 and so closing the circuit through the interrupter I.

In all these arrangements of apparatus itv will be seen that when telephoning is to be carried on, periodic amplitude variations, of a frequency above the limits of audibility, are impressed upon the high-frequency Waves, and that when it is desired to telegraph, there is added an interrupter, which breaks up the waves into groups or sets, the set fre uency being of a lower order than either t e frequency of the amplitude variations or that of the high-frequency waves.

In Figure 4 there is shown a receiving station with three different sets of receiving circuits, corresponding to the three transrnitting sets shown in Figure 1. The antenna B has three tuned'circuits, B L C E B L C E and B L C E The circuit B L C E, containing the coil L and the variable condenser C is in resonance with the high-frequency alternator H, of Figure 1, and also with the circuit L C". with which it is inductively connected by means of the coils L and IN. The rectifier .R and the stopping condenser D permit unidirectional current impulses of the'frequency of the variations in wave amplitude caused by the generator G of Figure 1 to pass through coil L, and when circuit L (3* P L is in resonance with this latter frequency, currents will be induced in it by means of the coils L and L, and telephone conversation from the transmitter T of Figure 1 can be heard at telephone receiver 1. When'the telegraph key K and interrupter I of Figure 1 are working, unidirectional current impulses will be induced in the untuned circuit L? R L by means of the coupling coil L and the rectifier R will cause current impulses of the frequency of the interrupter I to be impressed upon the circuit L C I, which is tuned to the frequency of the interrupter I, and telegraph signals will be received in the telephone P.

The other two receiving sets of Figure at operate in a similar manner, and need not be explained in detail. In a second receiving set, L L L, L L, L and L are inductance coils, C and C are variable condensers, D is a stopping condenser, E and R are rectifying detectors and P and P are telephone receivers. The circuits of this receiving set are tuned so thatit will be operated by a second transmitting set, say the one including the are 0, the key K and the telephone transmitter T. In a third receiving set, L L, L L L, L and I are inductance coils, C, C and C are variable condensers, D is a stop-ping condenser, R and R are rectifying detectors, and P and P are telephone receivers. The circuits of this receiving set are tuned so that it will respond to a third transmitting set, say the one including the generator H, the key K and the telephone transmitter T By means of the apparatus here shown, three telephone conversations can be carried on simultaneously, or three telegraph messages can be sent, or any combination of three telephone and telegraph messages. The circuits of each receiving set are in tune with the wave frequency, the amplitude variation frequency and the wave group frequency of the corresponding transmitting set. The three characteristic. frequencies of each transmitting and receiving set may all be different from the characteristic frequencies of the other sets, or only one or two characteristic frequencies may be different, the otherfrequency being the same for two or more sets.' Thus, .the same wave .lengfi might be used for all three sets, and

selectivity secured by having ,difi'erent rates of amplitude variation and wave-group frequency, V

A higher degree of selectivity could be secured by introducing an' additional amplitude variation or wave-group frequency in each set by means of an additional interrupter or insome. other'appropriate way, and it is also evidentthat, while three sets of apparatus are s'hownin this application, my invention is not confined to three sets,

but that two, four, or any number of sets of apparatus may be employed. In this application there are shown three difierent varieties of transmitting apparatus, but it is evident that the three sets might be the same, or that two sets might be the same,

a plurality of telephone or telegraph messages, since the methods and apparatus defined in man of the appended claims can be utilized in systems designed for the transmission and reception of a single message at a time.

What I claim as my invention and desire to secure by U. S. Letters Patent is:

1. A method of multiplex radio telephony. which consists in impressing telephonic vibrations upon a plurality of electric waves having different lengths and different amplitude variations, radiating said waves from'an antenna, and receiving them upon circuits tuned to the respective wave lengths and amplitude variation frequencies.

2. A method of radio telephony which consists in impressing telephonic virbrations upon a combination of electric waves and electric Wave groups, radiating said Waves and wave groups from an antenna, and receiving them upon circuits tuned to wave lengths and grou frequency.

3. A method 0 multiplex radio telephony which consists in generating high-frequency electric waves, impressing upon said waves periodic amplitude var ation-s having a frequency above the limits of audibility but different from the frequency of said waves,

' super-posing telephonic vibrations upon said waves and said amplitude varlations, radiating said waves from an antenna, and receiving them upon circuits tuned to the rea'spective wave frequencies and amplitude variation frequencies. s

4. A method of multiplex radio telephony which consists in transmitting telephonic vibrations by means of a plurality of electric waves ina plurality of series of groups, and receiving said vibrations on telephone re.-

ceivers connected with circuits tuned to wave lengths and group frequencies. y

'5. In a system of multiplex radio telephony, means for transmitting waves having different lengths in sets said waves having amplitude variations of different frequencies. said amplitude variations being independent of the telephonic vibrations.

6. In a system of selective radio telephony, means for generating high-frequency electric waves and for impressing upon said waves amplitude variations having frequencies above the limits of audibility, means for superposing telephonic vibrations upon said waves and said amplitude variations,

and a plurality of receiving circuits tuned to wave length and to amplitude variation frequency.

7. In a system of telegraphy and telephony, transmitting means comprising a source of high frequency electric waves, means operative either to impress telephonic vibrations on said Waves, or to interrupt said waves to form telegraphic signals, and a transmitting element arranged to be energized by said last mentioned means to emit either telegraphic .or telephonic mes sages. g

8.- In a systemof telegraphy and telephony transmitting-A means, comprising 9. sources of. high frequency electric waves, means operative either-to impress telephonic vibrations on said waves, or to form said waves into sets at a given set frequency andto interrupt said sets of waves to form telegraphic signals, and a transmitting element arranged to'be energized by said last mentioned means to emit either telegraphic ortelephonic messages.

9. In a system of telegraphy and telephony, transmitting means comprising a source of high frequency electric waves, means for forming said waves into groups. having a given group frequency, means operative either to impress telephonic vibrations on said groups or to divide said groups into sets and to interrupt said sets to form telegraphic signals, and a transmitting element arranged to be energized by said last mentioned means to emit either telephonic.

having .a given group frequency above the limits of audibility, means operative either to impress telephonic .vibrationson sald groups -orto divide said groups into sets and to interruptsaid sets to form telegraphic signals, and an antenna arranged to be energized by said last mentioned means to emit either telephonic or telegraphic messages.

11. A method of radio signalling ,which consists in generating a series of electrical oscillations having a predetermined frequency, producing in said oscillations periodic variations having a frequency different'from said first mentioned frequency and above the wave frequency of -,a tone of maximum audibility at a fixed amplitude, causing said oscillations thus varied to produce corresponding radiant oscillations, receiving said radiant oscillations upon cooperating receiving elements tuned to said frequencies respectively, and producing from time to time further variations in said electrical oscillations in order to form signals.

consists in generating a series of electrical oscillations having a predetermined frequency, producing in periodic variations having a frequency different from said first mentioned frequency and above audibility, causing said'oscillations thus varied to produce. corresponding radiant oscillations, receiving said radiant oscillations upon cooperating receiving ele ments tuned to said frequencies respectively, and producing from time to time further variations in said electrical oscillations in order to form signals. v

13. A method of radio signalling which consists in generating a series of electrical oscillations having a predetermined frequency, producing in said oscillations periodic amplitude variations having a frequency different from said first mentioned frequency and above the Wave frequency of a tone of maximum audibility at a fixed amplitude, causing said oscillations thus varied to produce corresponding radiant oscillations, receiving said radiant oscillations upon cooperating receiving elements tuned to saidfrequencies respectively, and producing from time to time further variations insaid electrical oscillations in order to form signals.

14. A method of radio signalling which consists in generating a series of electrical oscillations having a predetermined frequency, producing in said oscillations periodic amplitude variations having a frequency different from said first mentioned frequency and above audibility, causingsaid oscillations thus varied to produce corresponding'radiant oscillations, receiving said radiant oscillations upon cooperating receiving elements tuned to said frequencies respectively, and producing from timeto time further variations in said electrical oscillations in order to form signals.

15. Ina system of signaling, means for generatinga series of high frequency electric Waves and for impressing upon sa1d waves periodic variations having a frequency above audibility, means for modifying said waves and said periodic variatlons from time to time to form slgnals, and

means for receiving said signals comprising a plurality of receiving elements tuned to the frequency of said waves and the frequency of said variations respectively.

16. In a system of signaling, means for generating a series of high frequency electric waves and for impressing upon said waves periodic amplitude variations having a frequency above the upper limits of audibility, means for modifying said waves and said periodic amplitude variations from time to time to form signals. and means for receiving said signals comprising a plurality of receiving elements tuned to the frequency said oscillations mamas combination with a circuit of means c00perating therewith for causing said circuit to transmit a plurality of series of hi h frequency waves, of means for perio ically varying the amplitude of the waves in each series, and means operative either to form the waves of each series into sets of groups of waves or to impress telephonic vibrations on each series.

18. A system comprising means for generating periodic impulses having a predetermined frequency and for producing in said impulses either simultaneously or selectively a plurality of series of periodic variations having different predetermined frequencies respectively, each of said last men-' tioned frequencies being different from said first mentioned frequency, and means for rementioned circuits respectively.

19. A method of radio signaling which consists in generating a series of electrical oscillations having a predetermined frequency, producing in said oscil lations periodic variations having a frequency different from said first mentioned frequency and substantially above audibility, causing said oscillations thus varied to produce corresponding radiant oscillations,

receiving said radiant oscillations upon 00- operating receiving elements tunedto said frequencies respectively, arid producing from time to time further variations in said elelctrical oscillations in order to form signa s.

20. A method of radio telephony which consists in generating high frequency electric waves, impressing upon said waves periodic, variations having a frequency above the limits of audibility and different from the frequency of said waves, superposin tele honic vibrations upon said waves an variations, radiating said waves from an antennayand receiving said radiated waves upon cooperating circuits tuned to the frequency of said waves and to the frequency of said variations respectively.

21. In a system of radio telephony, means for generating a series of high frequency electric waves and for impressing upon said waves periodic variations having a frequency above the upper limits of audibility,

means for modifying said waves and said periodic variations from time to time to 1 modulated at a, plurality of frequencies,

' one of said form signals, and means for receiving said signals comprisin'gia plurality of receiving elements tuned to the frequency of said waves and the respectively.

' 22. A carrier. wave transmission system means arranged to be controlled by the received energy for producing a'current of electrical impulses having a frequency corresponding to one of said first mentioned frequencies and means arranged to be con-2 trolled by said current of electrical impulses for producing a: current of electrical impulses having a frequency corresponding to another of said first mentioned frequencies. 24. The combination with a transmission system including means for transmitting. a series of waves modulated at a plurality of frequencies, of a receiving system including means for receiving the energy of said modulated waves and means controlled by said receiving means for producing as a result of the action of said energy, a current of electrical impulses having a frequency corresponding to one of said first mention'edfrequencies, and means arranged to be controlled by said current of electrical impulses for producing a current of electrical impulses having a frequency corresponding to another of said first mentioned frequencies. 25. The combination with means for transmitting impulses having an inaudible frequency modulated at a substantially inaudible second frequency and also at an audible frequency, of means for receiving the energy of said audible frequency.

26. A system of signalling comprising means for producing impulses lnclud ngl twoseries of impulses having different subfrequency of said variations impulses thus modulated, 'demodulating means controlled by said received energy for by said last mentioned impulses for stantially inaudible frequencies respectively in yc'ombination with receiving means responsive to said impulses, and receivin means controlled by said first mentione receiving means and tuned to respond to the lower one of said two series of impulses.

27. In a selective system of transmission of electric waves, a transmitter comprising means for radiating high frequenc electric waves, and-for producing in said liigh frequency electric waves a periodically recurring variation of the emitted energy, the period of said variation of energy be1ng independent of the high frequency oscillations.

of the said wave, and a'receiving station containing a circuit energized *bysaid .independent energy variation of the {transmitter, said circuit having a period uninterfe'r:

able by said high frequency oscillations or' oscillations of audible frequency.

v 28. In a selective system for the transmission of electroradiant energy, the combination with transmission means arranged to emit electroradiant oscillations of apredeterminedhigh frequency, and to impress on said oscillations a plurality of series of periodic variations of different predeter-' mined frequencies, of receiving means arranged to selectively receive said oscillations and sa1d variations and to function through the conjoint action of said oscillations and said plurality of series of variations.

I 29. system in accordance with claim 28, 1n which the receiving means functions of the said oscillations and said plurality of series of variations. j

30. In a selective system for the transmissionof electroradiant energy, the combination withtransmission means arranged to emit a. series of sets of groups of electroradiant oscillations of a redetermined high through the conjoint and successive action frequency having a pre etermined set -frequency and a predetermined group frequency, of receiving" means arranged to selectively receive said oscillations and to function through the conjoint action of said oscillations, said groups and said sets.

- 31. A system in accordance with claim 30,

in :which the receiving means functions through the conjoint and successive action of-the said oscillations, said groups and said sets. a

32. The method of transmitting and receiving radiant energy which consists in emitting sets of groups of electroradiant oscillations having a predetermined set frequency, a predetermined group frequency and a predetermined wave frequency oroscillation frequency, and selectively receiving said sets of groups of oscillations, and causing'the performance of a function as a result of the conjoint action of said oscillations, said groups and said ets.

ries having a frequencyabove audibility and the other of said series having a frequency within the limits of audibility, and causing the functioning of a receiving device as the result of the conjoint and successive action of said oscillations and said periodic variations.

35. A system for transmitting and receiving radiant energy, comprising means for emitting a series of electroradiant impulses having a frequency substantially above audibility, and having impressed therein a series of periodic modifications having a frequency different from said first-mentioned frequency and substantially above audibility, in combination with means for receiving said impulses and modifications including two elements tuned to respond selectively to said impulses and modifications respectively and a receiving device arranged to be controlled by the conjoint action of said elements.

36. A system in accordance with claim 35 in which one of said elements is in the form of an electrically tuned circuit.

37 A system in accordance with claim 35, in which each of said elements is in the form of an electrically tuned circuit.

38. A system in accordance with claim 35, in which said elements are arranged to act successively.

' 39. A system in accordance with claim 35, in which said receiving device is tuned to an audible frequency.

40. A system in accordance with claim 35, in which said receiving device is in the form of a circuit tuned to res 0nd to electrical impulses of a frequency di erent from either of said first-mentioned frequencies.

41. A system in accordance with claim 35, in which said elements are arranged to act successively and said receiving device is tuned to respond to electrical impulses of a frequency different from'eitherof said first mentioned frequencies.

42. A system in accordance with claim 35 in which said elements are arranged to act successively and said receiving device is tuned to respond to impulses of an audible frequency.

43. A selective system of wave transmission and reception comprising means for transmitting waves having a predetermined frequency, means for impressing in said waves a plurality of series of periodic variations having different frequencies respec tively, and means for selectively receiving said waves and variations including a plurality of cooperating elements tuned to the frequency of said waves and the frequencies of a. plurality of-said variations respectively, said elements being arranged to act successively.

44. A system in accordance with claim 43, in which each of said elements is in the form of an electrically tuned circuit.

45. A selective system of wave transmission and reception, including means for transmitting waves having a frequency above audibility, means for impressing in said waves two series of periodic variations,'one of said series of variations having a frequency above audibility and the other of said series of variations having a frequency within audibility, and means forreceiving said waves and variations including two cooperating elements tuned to said two firstmentioned frequencies respectively and a third element controlled by said first-mentifined elements and tuned to said thirdmentioned frequency respectively.

46. The method of transmitting and receiving energy, which consists in transmitting a series of waves having a frequency substantially above audibility, impressing in said waves a series of periodic modifications having a frequency different from said firstmentioned frequency and substantially above audibility, selectively receiving said waves and variations, and controlling a receiving device as the result of the conjoint action of said waves and variations.

47. A method in accordance with claim 46, and in which the receiving device-is controlled as a result of the conjoint and successive action of said waves and variations.

48. A system for transmitting and receiving energy comprising means for generating a series of periodic impulses having a frequency substantially outside of the range of audibility and for impressing upon said impulses a series of periodic variations having a frequency different from saidfirst-mentioned frequency but substantially outside of the range of audibility, in combination with means for receiving said impulses and variations including two elements tuned to respond selectively to said impulses and vanations respectively, and a receiving device arranged to be controlled by the conjoint action of said elements.

49. A system in accordance with claim 48, in which the receiving device is controlled by the conjoint and successive action of said element.

50. A systemfor transmitting and receiving .radiant energy comprising means for transmitting radiant energy in a plurality of series of periodic impulses of different radio quency the radiant energy comprising a 'for generating electrical waves frequencies,and means for receiving-the radiant energy compris ng circuits tuned respectively to said series of impulsesand ar- 51. A system for transmitting and receiving radiant energy comprising means for transmitting radiant energy in aplurality of series of periodic impulses of different radio frequencies, and means forreceiving the radiant energy comprising circuits tuned respectively to said series of impulses and arranged to cause current to be supplied to one'of said circuits tuned to a lower frein response to the setting up of current of predetermined character in another of said circuits tuned to a higher frequency.

52. A system for transmitting and receiving radiant energy comprising means for transmitting radiant energy in a pluralityof series of periodic impulses of different radio frequencies, and means for receiving the radiant energy comprising a single antd'nna and a plurality of circuits tuned respectively to said series of impulses and connected in cascade arrangement with the antenna.

53. A system for transmitting and receiving radiant energy comprising means for transmitting radiant energy in a plurality of series of periodic impulses of different radio frequencies, and means for receiving the radiant energy comprising a plurality of cir-. cuits tuned respectively to said series of impulses and connected in cascade arrangement so that current is supplied to each succeeding circuit in response to the setting up of cur-- rent'of a predeterminedcharacter in the preceding circuit. 1

54. A system for transmitting and receiv-. ing radiant energy comprising means for transmittin radiant energy in a plurality of-series o periodic impulsesof different radiofrequencies, and means for receiving plurality of circuits qon'nected' in series and tuned respectively to'saidseries of impulses, rectifying means intermediate between certainof the adjacentcircuits, and a device controlled by the conjoint action of the impulses impressed upon said circuits. 4 55. A method of transmitting andreceiving radiant energy which consistsin' transmitting radiant energy as a' lurality of series cf periodic impulses of di erent radio frequencies, pulses with rectification of one of -said series j to bring out im f said series, and contro ling .a receivin as. a result of the conjoint action 6 ulses.

56. A system of signaling includin'gimeans, having a ing device responsive tel-mined high frequency,

selectively receiving saidj imfixed frequency characteristic and variable speech frequency characteristic, an indicatto the speech frequency characteristic of said waves, means for. im-

pressing upon said waves an additional fixed frequency characteristic to which said indicating device is unresponsive, and an element co-acting with the tuned to the frequency of said additional fixed characteristic so as to increase the selectivity; with which the speech signals may be received.

indicating device and 57 -A system of signaling including means for generating electric waves having a fixed radio frequency characteristic and a variable speech frequency characteristic, an indicating device responsive tothe'speech frequency characteristic of said waves, means for impressing upon said waves a different fixed frequency characteristic to which said indicating-device is unresponsive, and. a circuitco-acting wlth the .lIldIGfitlIlg device and said'difierent fixed tuned to the frequency of the selectivity characteristic so as to increase with which the speech signals may be received.

58. A system of signaling including means responsive to electric waveshaving a predemeans for impressing speech frequency variations upon said waves, an indicatingdevice responsive to said speech frequency impressing upon said waves additional frequency variations differing both fromthe first-mentioned frequency and from the speech frequency variations, said indicating device being unresponsive to said additional variations, and an-element co-acting with the indicating device of said additional variations so as toincrease 'the selectivity with which the speech signals 'may be received. I 59. A system of signaling including-means variations, means for and tuned to the frequency for generating electrical oscillations having a predetermined frequency, means for impressing speech frequency variations upon said oscillations, an indicating device responsive tov said speech frequency variations, means for impressing periodic amplitude variations having a frequency intermediate the frequency of said oscillations and sald speech frequency variations, and a circuit co-actmgwith the indicating device and electrically tuned to the frequency of said. periodic amplitude variationsso as to increas the selectivity with which the speech signals maybe received.

60. The combination in awireless signaling system of means gle series of signals by waves of two different radio frequencies simultaneously radiated from an antenna, and a receiving stai101! havlng means for receiving th waves,

means for producing from fthem a current having a frequencyfor transmitting a smlessjthan the higher iof upon said oscillations said two different radio frequencies and determined by said radio frequency Waves, said last-mentioned current being above audibility, an oscillating circuit resonant to said last-mentioned current, and means cooperating with the oscillating circuit for detecting the signals.

61. The combination in a wireless signaling system of means at a transmitting station for producing radio frequency currents having definite amplitude pulsations of a frequency above audibility, a receiving station having means for receiving signals transmitted by the currents thus produced at the transmitting station, means for changing the radio frequency currents received by this antenna to an alternating current of a frequency corresponding to the amplitude pulsations of the currents produced atthe transmitting station, and means for the selective reception and detect-ion of this current. I

62. The combination in a Wireless signaling system of transmitting apparatus comprising a source of. energy of radio frequency including a second controlling source of energy of substantially lower frequency but above audibilit for controlling the flow of current from t e radio frequency source so as to produce amplitude pulsations therein of a frequency equal to that of the controlling source, means for transmitting waves of two different radio frequencies derived from the current having amplitude pulsations, means for impressing a single series of signals on said waves, means at a receiving station for receiving the waves of two radio frequencies and producing from them an alternating current of a frequency corresponding to the frequency of the controlling source in the sending station, and means for the selective reception and detection of the current thus produced.

63. A receiving system for waves comprising a plurality of successively responsive circuits connected together in cascade relation and tuned respectively to a plurality of wave group frequencies, and a device arranged to be' actuated in response to the conjoint action of a plurality of said circuits.

64. In a system of wave transmission, the combination with means for transmitting a plurality of series of groups of waves of different group frequencies, of receiving neans comprising a plurality of cooperatmg elements, connected together in cascade relation and tuned to said frequencies re spectively, and a device arranged to be actuated in response to the combined action of a plurality of said elements.

65. The combination with means for transmitting waves having a predetermined high frequency, of means for impressing on said waves a series of per1od1c amplitude meagre variations havin a frequency less than said first-mentioned requency, means for dividing said waves into groups or sets having a frequency less than the frequency of said amplitude variations, and means for receiving said waves including three elements tuned to respond to said three' frequencies rdspectively, and a receiving device-s arranged to be controlled by the conjoint action of said elements.

66. A method of wave which consists in transmitting a series of electroradiant waves having a predetermined high frequency above the limits of audibility, impressing upon said Waves a plurality of series of periodic variations having different predetermined frequencies, one of said series of variations having a frequency less than said first-mentioned frequency but above the limits of audibility. and other of said series of variations having a frequency within the limits of audibility, receiving said waves on a plurality of cooperating elements t-uned to respond selectively to said first-mentioned frequency and to said second-mentioned frequencies, and controlling a recelvlng device as a result of the conjoint action of said elements.

67. In a radio transmission system, the combination with means for producing continuous radiant impulses of a predetermined frequency of means separate from said producing means and operative to impress upon said impulses a series of periodic variations having a frequency different from said first-mentioned frequency, and means automatically operative to interrupt said impulses periodically at a frequency different from said first-mentioned frequencies.

68. A system of radio signaling which comprises a source of high frequency oscillatory energy, means for transmitting .said oscillatory energy, a receiver for said energy, means for producing current at the receiver havinga predetermined frequency above audibility but lower than the frequency of said oscillatory energy, said lastmentioned means including a source of high frequency energy arranged to cause its energy to be combined with said high frequency oscillatory energy, means for detecting said current, and means for indicating the current. p

69. A method for securing selectivity in electric wave transmission which consists in transmitting waves of different definite wave lengths in'groups at different definite group frequencies and transmitting the wave groups insets at different definite set rates. a

70. In a selective signaling system, a receiving circuit tuned to the wave frequency of a high frequency signal wave having a low frequency component, a second circuit tuned to an intermediate frequency above transmission.

audibility and-connected in cascade rela-- tion with said first-mentioned circuit, means for producing current of said intermediate frequency, said means including-a detector interposed between said circuits and a sourceof electrical oscillations arranged to combine its energy with the energy of the signal wave, and an indicator associated with said secondcircuit.

71. A multiplex transmission system for radiant'energy, comprising means for emitting a series of'radiant oscillations having a predetermined frequency, a plurality of separately operative devices for impressing on said oscillations a lurality of series of periodic modifications having difi'erent predetermined frequencies respectively, and means included in each of a plurality of said devices for impressing a separate series of variations corresponding to 'sound waves on said oscillations in connection with each of a plurality of said series of modifications,

7 In a selective signaling system, a receiving circuit tuned to the wave frequency of a high frequency signal wave having a fixed wave frequency characteristic and a va-- ri able speech frequency characteristic, an indicating device responsive to the speech frequency characteristic of said waves, means for impressing upon said waves an additional fixed frequency characteristic to which said indicating device is unresponsive, said means includin a source of electrical oscillations arrange to combine its energy with that of the signal wave, and a circuit co-acting with the indicating device and conductive only to currents of the frequency of said additional fixed characteristic.

73. In a selective signaling system, a receiving circuit tuned to the wave frequency of a high frequency signal wave having a fixed wave frequency characteristic and a variable speech frequency characteristic, an indicating device responsive to the speech frequency characteristic of said waves, a second circuit tuned to a predetermined frequency above audibility but lower than the frequency of the signal wave and connected in cascade relation with said first-mentioned circuit and with said indicating device, and

-means for producing current of said lastmentioned frequency in said second circuit under the control of the signal wave, ,said means including a detector interposed. be-

tween said circuits and a source of electri-' cal oscillations arranged to combine its energy with the energy of the signal wave.

4- In a selective signaling system, a receiving circuit tuned to the wave frequency of a high frequency signal wave, a second circuit tuned to a predetermined frequency above audibility but lower than the frequency of the signal wave and connected in joint action of said high frequepcg 1 cascade relation with saidfirst-mentioned circuit. means for producing current of said last-mentioned frequency, said means including a detector interposed between said circuits and a source of electrical oscillations arranged to combine its energy with the energy of the signal wave, and an indicator associated with saidsecond circuit.

75. In a selective signaling system, a receiver for oscillatory energy, means for producing currentat the receiver having a pre- -a low frequency component, means includ- -1ng a source. of electrical osclllatlonsof superaudible frequency for producingin connection with said high frequency waves an additional component differin in frequency both from the first named frequency and from the frequency of said low frequency component, a tuned circuit adjusted torespond to said differing frequency, a detector controlled by said circuit element, and an indicating device operable only by the conwaves and said additirnal component 0 flering frequency, said indicating device being unresponsive to said difl'ering frequency.

77. In a system of tele hony, means selectively responsive to'hig frequency electrical oscillations having telephonic vibrations superposed thereon, means for producing in connection with said oscillations additional frequenc variations differing both from the high requency oscillations and from the telephonic vibrations, means tuned to respond only to said additional frequency variations, a detector controlled by said vtuned means, a' d an indicating device controlled by said detector.

78. In a system of telephony, means selectively responsive to high frequency electrical oscillations having telephonic vibra tions superposed thereon, means for producing in connection with said oscillations ad ditional frequency variationsdifl'ering from the high frequency oscillations and above audibillty, a detector, an indicating device controlled by said detector, and means for' impressing on the input of said detector only currents of substantially said additional frequency.

79. In a system of communication utilizing a signal wave comprising high frequency electrical oscillations having variations corresponding to signals superposed thereon, indicating device controlled by said last 1 means including a source of energy for named detector. H forming said waves into groups having a This specification signed and witnessed git 1mg 1group friequency FbOVG the hlimitsf of this 9th day of May A. 11,1912. 5 an i iity, a etector or saidigh .re 1

quency waves, a detector for said group of JOHN HAYS O waves, a circuit interposed between said de- Witnesses: tectors and conductive only to currents of M. P. WINNE, the frequency of said groups, and a signal D. F. Duane. 

